Hydrogenated elastomer primed polyolefin film

ABSTRACT

A pressure-sensitive tape is provided having a polyolefin backing, a primer comprising an elastomeric block copolymer which primer is applied from a non-aromatic hydrocarbon solvent, said tape further comprising an adhesive on the thus primed surface. Because the primer is laid down from a solution in a non-aromatic hydrocarbon solvent such as methyl cyclohexane the process utilizes an environmentally-friendly solvent.

BACKGROUND OF THE INVENTION

This invention relates to primed polyolefin films.

Frequently it is desirable to utilize a primer or tie-coat between afilm substrate and an adhesive. Historically, solutions of materialssuch as NEOPRENE rubber and an aromatic solvent such as toluene havebeen used. However, environmental concerns encourage substitution ofnon-aromatic solvents. Excellent substitute solvents such as those basedon hydrogenated toluene are available, but they do not adequatelydissolve NEOPRENE rubber.

SUMMARY OF THE INVENTION

It is an object of this invention to provide a primed polyolefin filmsubstrate;

It is a further object of this invention to provide an improved processfor producing a primed polyolefin film substrate;

It is yet a further object of this invention provide a polyolefinpressure-sensitive tape without the use of aromatic solvents; and

It is still yet a further object of this invention to provide apolyolefin substrate primed using an environmentally-friendly primersolution.

In accordance with this invention a polyolefin film substrate is primedwith a hydrogenated elastomeric block copolymer dissolved in anon-aromatic hydrocarbon solvent.

DETAILED DESCRIPTION OF THE INVENTION

Applicants have found that toxicity problems and environmental problemswith NEOPRENE primer solutions for polyolefin film substrates can beavoided and better adhesion obtained by using a non-aromatic hydrocarbonsolution of an elastomeric block copolymer which has been hydrogenated.

The elastomeric block copolymers suitable for use herein are known inthe art as disclosed for instance in Stevens et al. U.S. Pat. No.5,194,530 (Mar. 16, 1993) the disclosure of which is hereby incorporatedby reference. Suitable polymers for use in this invention haveend-blocks made of polymerized monovinyl aromatic compound thus giving aresinous segment and a mid-block made up at least predominantly ofpolymerized conjugated diene monomer thus giving an elastomeric segment.The polymers can be linear ABA, or radial or mixtures thereof. Some ABdiblock polymer can be present but at least 20, preferably at least 60weight percent of the block copolymer is ABA or radial (or otherwisebranched so as to have two or more terminal resinous blocks permolecule) so as to impart strength. Generally, 80-100 weight percent hastwo or more terminal resinous blocks per molecule.

Suitable monovinyl aromatic compounds are those having 8 to 20 carbonatoms as exemplified by styrene and styrene homologs such asalpha-methylstyrene and para-methylstyrene. Styrene is especiallypreferred. Suitable conjugated dienes include those having 4 to 8 carbonatoms. Illustrative of such conjugated dienes are 1,3-butadiene(butadiene), 2-methyl-1,3-butadiene (isoprene), 1,3-pentadiene(piperylene), 1,3-octadiene, and 2-methyl-1,3-pentadiene. Preferredconjugated dienes are butadiene and isoprene.

The end-block segments (A) preferably have a molecular weight of atleast 5000, preferably 5000 to 18,000, more preferably 7000 to 10,000.Endblocks of 5000 to 15,000 are also highly suitable. The monovinylsubstituted aromatic compound component must be present in an amount ofat least about 8 weight percent based on the total weight of thepolymer. Generally, 13 to 40 weight percent aromatic component,preferably 20 to 40 weight percent aromatic component is utilized. Theweight percentages are based on the weight of the total polymer. Themolecular weight of the total polymer can vary considerably butgenerally will be within the range of 40,000 to 300,000, preferably60,000 to 180,000. By molecular weight as it refers to linear polymersis meant the molecular weight as measured by gel permeationchromatography (GPC), where the GPC system has been appropriatelycalibrated with known polystyrene standards. For anionically polymerizedlinear polymers, the polymer is essentially monodispersed and it is bothconvenient and adequately descriptive to report the “peak” molecularweight of the narrow molecular weight distribution observed. Suchmethods are well known and described in patents including U.S. Pat. No.5,229,464, the disclosure of which are hereby incorporated by reference.

Measurement of the true molecular weight of a final coupled star orradial polymer is not as straightforward or as easy to make using GPC.This is because the star-shaped molecules do not separate and elutethrough the packed GPC columns in the same manner as do linear polymersused for the calibration, and, hence, the time of arrival at a UV orrefractive index detector is not a good indicator of the molecularweight. A good analytical method to use for a star polymer is to measurethe weight average molecular weight by light scattering techniques. Thesample is dissolved in a suitable solvent at a concentration less than 1gram of sample per 100 milliliters of solvent and filtered using asyringe and porous membrane filters of less than 0.5 microns pore sizedirectly into the light scattering cell. The light scatteringmeasurements are performed as a function of scattering angle and ofpolymer concentration using standard procedures. The differentialrefractive index (DRI) of the sample is measured at the same wave lengthand in the same solvent used for the light scattering. This results in amolecular weight value which approximates weight average molecularweight.

The elastomeric block polymers utilized in this invention are furtherhydrogenated to such a degree that the unsaturation of the elastomericblock is greatly reduced without significant hydrogenation of thearomatic unsaturation in the “A” block component. Generally, at least 90percent, preferably at least 98 percent more preferably at least 99percent, of the unsaturation in the diene center block is hydrogenatedand no more than 25 percent, preferably less than 10 percent of thearomatic unsaturation is hydrogenated. Such hydrogenation techniques areknown in the art and disclosed, for instance, in Jones Reissue U.S. Pat.No. 27,145 (Jun. 22, 1971) the disclosure of which is herebyincorporated by reference. Thus, for instance, with one of the preferredblock copolymers, styrene-butadiene-styrene, the resulting hydrogenatedpolymer (because of the 1,2-addition) can be viewed as astyrene-ethylene/butene copolymer-styrene. Similarly, another preferredblock copolymer, styrene-isoprene-styrene linear block copolymer can beviewed as a styrene-ethylene/propylene copolymer-styrene block polymer.

The thus hydrogenated elastomers can be used as such in this inventionbut are preferably functionalized by treatment with an unsaturatedmonomer having one or more functional groups or their derivatives suchas carboxylic acid groups and their salts, anhydrides, esters, imidegroups, amide groups, and acid chlorides in addition to at least onepoint of unsaturation.

The preferred monomers to be grafted onto the block copolymers to givethe functionalized polymers utilized in this invention are maleicanhydride, maleic acid, fumaric acid, and their derivatives. It is wellknown in the art that these monomers do not polymerize easily. A furtherdescription of functionalizing selectively hydrogenated block copolymerscan be found in Gergen et al. U.S. Pat. No. 4,578,429 (Mar. 25, 1986)the disclosure of which is hereby incorporated by reference.

The resulting grafted polymer will usually contain from 0.02 to 20preferably 0.02 to 5 or 2 to 5, and most preferably 0.2 to 2 weightpercent grafted portion based on the weight of the total polymerincluding the grafted portion.

Thus the primer composition of this invention comprises the hydrogenatedelastomeric block copolymer and the solvent. While the compositions cancontain other components such as oils, end-block resins and tackifiersfound in adhesives compositions they generally consist essentially ofthe elastomeric block copolymer and the solvent. Generally, nocrosslinking agents are used. This, of course, does not exclude thepresence of materials such as stabilizers which are used for the normalpurpose of stabilization of the elastomer.

The solvent used in this invention is a non-aromatic hydrocarbon. Aparticularly preferred solvent is one made up predominantly ofmethylcyclohexane which is preferably obtained by the hydrogenation oftoluene. Such solvents can be produced by hydrogenation of thecorresponding aromatic component, i.e. benzene to cyclohexane or can beproduced by other known chemical means. Also, naturally occurringnon-aromatic hydrocarbons in petroleum streams can be separated andpurified for use in this invention. The production of the preferredcomposition which is predominantly hydrogenated toluene, i.e.methylcyclohexane, along with other aliphatic hydrocarbons species, isdescribed in Shell Brochure SC:2304-95. Typically these solvents have aboiling point with the range of 93 to 132° C. (200 to 270° F.).

The polyolefin can be any of the known film-forming olefin polymers suchas polypropylene, polyethylene, and ethylene higher alpha-olefincopolymers such as ethylene/butene, ethylene/pentene, ethylene/hexene,and ethylene/octene copolymers.

Preferably, these polymers, when formed into film, are oriented so as togive additional strength due to the molecular alignment of themolecules. Polymer can be oriented by rapidly drawing during theformation at about the temperature that crystallization occurs.Alternatively, the film can be reheated to just below the crystallinemelting point and stretched. In a particularly preferred embodiment thefilm is biaxially oriented, that is stretched in both longitudinal andtransverse directions. Orienting on the heating cycle is much easierbecause there is a broad temperature window during which significantamounts of the crystals have melted but some have not which is a goodorientation temperature, whereas on the cooling cycle the materialcrystallizes so quickly that it goes through the orientation temperaturetoo fast. Biaxial orientation can be effected with blown film simply bycooling, reheating and blowing the film to a larger diameter than theextrusion annulus and, optionally, at the same time pulling the film ata more rapid rate than the rate of extrusion. Flat film is generallyoriented by extruding or calendaring after which it is rolled up andthen oriented longitudinally by drawing between sets of heated rollsrunning at different speeds. The first roll heats the film toorientation temperature and the second pulls it at a faster speed toeffect longitudinal orientation. Thereafter the film the gripped at theedges by a tethering frame and moved through an oven where it is heatedto orientation temperature and stretched transversely. Alternatively,the transverse orientation can be first or both can be done at oncewhich is preferred but more complicated from a mechanical standpoint.Even with biaxial orientation there is generally greater orientation inthe longitudinal direction (especially with flat film) and such film isideally suited for materials such as packaging tape which utilizes theextremely high tensile strength generated in the longitudinal direction.A particularly preferred material is biaxially oriented polypropylenefilm.

Film thickness can vary depending on the desired application. For tapeapplications the thickness is generally within the range of 0.000254 to0.0254 cm (0.1 to 10 mil), preferably 0.00127 to 0.0127 cm (0.5 to 5mil), more preferably about 0.00254 to 0.00508 cm (1-2 mil). Such filmsare, of course, commercially available.

The surface treatment, if utilized, can be carried out in a manner knownin the art. One commonly used technique is to utilize a corona dischargewhich oxidizes this surface. Another common technique is to utilize anacid treatment; alternatively flame treatment can be utilized althoughthis is more commonly practiced with thicker work pieces. Nonetheless,these are all well-known commercial techniques which can be utilized ifdesired.

Since the solvent will be evaporated away, the concentration is notcritical but generally solutions of from 1 to 30, preferably 5 to 20,more preferably 5 to 10 weight percent solids are utilized. The reasonfor relatively dilute solutions is to allow even application of arelatively thin primer coat and the fact that the elastomer tends tothicken the solution too much at higher concentrations. The solutionscan be applied utilizing standard equipment for applying thin coatingsof liquids on substrates. For high-speed commercial operations aconventional roll-coater or knife-blade coater would generally be used.With a roll-coater, the solution is applied to a roll which contacts themoving polyolefin film substrate and transfers a thin coating of thesolution to the surface of the substrate. Knife-blade coating involvesspreading out a thin film of coating solution with a flat blade. All ofthese techniques are well-known in the art. Primer coatings having athickness to 0.000127 to 0.00254, preferably 0.000127 to 0.00127, morepreferably 0.000254 to 0.000501 cm (0.05 to 1, preferably 0.05 to 0.5,more preferably, 0.1 to 0.2 mils) are utilized.

The adhesive can be any known pressure-sensitive adhesive but ispreferably a composition comprising an unhydrogenated elastomeric blockcopolymer and a tackifier. Preferably it also contains oil, a mineralfiller and an antioxidant.

The elastomeric block copolymer can be of the same scope as that blockcopolymer described hereinbefore with regard to the primer except thatit is preferably not hydrogenated. This is because the unhydrogenatedmaterial is less expensive and provides better tack. Because of thealiphatic unsaturation, it generally requires a stabilizer, however.

The tackifier is preferably one which is compatible with the elastomericmid-block section and does not go into the aromatic resinous end-blocksections to any significant extent. The type of resins which aremid-block compatible are known in the art and are described, forinstance, in Allison U.S. Pat. No. 4,360,568 (Nov. 23, 1982), thedisclosure of which is hereby incorporated by reference. These types ofmaterials go exclusively, or almost exclusively, into the rubberymid-block section, not just because it is rubbery but also because it isa non-aromatic component. Hence, these materials are aliphatic compoundswhich is meant to include both hydrocarbons and materials such asesters. Hence, the tackifier may be a straight-chain hydrocarbon, suchas polymerized olefin sold under a tradename such as Wingtack® 95(Wingtack 95 is prepared by the cationic polymerization of 60%piperylene, 10% isoprene, 5% cyclopentadiene, 15% 2-methyl-2-butene andabout 10% dimer, as taught in U.S. Pat. No. 3,577,398) and SuperStayTac®. Others include hydrogenated mixed esters of polymerized rosinsold under the tradename Polypale®, hydrogenated glycerol esters ofrosin sold under the tradename Foral® 85, hydrogenated pentaerythritolesters of rosin sold under the tradename Pentalyn® H, polydipentene soldunder the tradename Zonarez® 7115, and polyterpenes. Other suitabletackifier resins can be produced by hydrogenating an aromatic componentso as to remove not only any vinyl or straight chain unsaturation butalso to remove most of the aromatic unsaturation. For instance, aparticularly preferred material is sold under the tradename Regalrez® byHercules.

The oil is preferably one which is compatible with the elastomericmid-block segment of the elastomeric block copolymer and does not tendto go into the aromatic resinous end-block portion to any significantdegree. Suitable oils include hydrogenated naphthenics. These containlow levels of aromatic unsaturation. A particularly suitable material isTufflo® 6056 sold by Witco. It is a hydrogenated naphthenic. Anotherpreferred oil is SF 371 from Shell.

The mineral filler can be any known mineral filler such as calciumcarbonate or titanium dioxide pigment (rutile alumina-treated). Othermineral fillers include clays, talcs, silica and zinc oxide. The mineralfiller serves to cheapen the formulations. Mineral filler, if present atall, can be present in an amount within the range of 1 to 20 or 1 to 10weight percent based on the weight of adhesive composition. The adhesivecan be applied from a hot melt or a solution of generally 30 to 65preferably 40 to 50 weight percent in a suitable solvent. The adhesivewill generally be applied so as to give a thickness of 0.00127 to 0.127,preferably 0.00178 to 0.00381 cm (0.5 to 5, preferably 0.7 to 1.5 mils).

Generally, the adhesive and optionally the primer will contain aconventional stabilizer or stabilizer system which frequently is simplyan antioxidant such as a hindered phenol. Particularly preferred isIrganox® 1010 which istetrakis-[methylene-3,5-di-t-butyl-4-hydroxyhydro-cinnamate)]methane.Suitable stabilizers are shown in Apalper et al. U.S. Pat. No. 5,149,741(Sep. 22, 1992), and St. Clair U.S. Pat. No. 4,835,200 (May 30, 1989),the disclosures of which are herein incorporated by reference. Dependingupon the severity of the conditions encountered in fabricating and use,more volatile materials such as 2,6-di-t-butylphenol may be utilized.Thiosynergists are less preferred because of possible odor problems.Stabilizers are generally present in an amount within the range of 0.01to 5, preferably 0.5 to 1 weight percent based on the weight of theprimer or adhesive composition exclusive of solvent.

The primer and adhesive compositions may further contain conventionalingredients which do not significantly affect the elastomeric oradhesive properties. Such optional ingredients include pigments,fragrances and other ingredients of adhesives.

EXAMPLES Example 1

7 weight percent solids in two solvents were prepared and cast ontocorona treated biaxially oriented polypropylene film and also cast onthe reverse side which was untreated polypropylene. The coating wascarried out in the machine direction. The formulations are set outhereinbelow in Table 1.

TABLE 1 Materials A B C D E F G H G1652¹ 7 7 0 0 0 0 0 0 FG1901² 0 0 7 70 0 0 0 B52-5³ 0 0 0 0 7 7 0 0 Bayprene⁴ 0 0 0 0 0 0 3.5 3.5 Nipol⁵ 0 00 0 0 0 3.5 3.5 Toluene⁶ 93 0 93 0 93 0 93 0 XPS6847⁷ 0 93 0 93 0 93 093 ¹KRATON ® R G1652 elastomeric ABA block copolymer; 7,200 MWpolymerized styrene end-blocks; mid-block hydrogenated 1-2 additionpolymerization butadiene; 28 weight % styrene SEBS ²KRATON ® G1652maleated to give about 2 weight percent functional component. ³KRATON ®G1652 maleated to give about 5 weight percent functional component.⁴Neoprene rubber. ⁵Neoprene rubber. ⁶Aromatic solvent. ⁷Developmentalnon-aromatic hydrocarbon containing predominantly methylcyclohexane andother aliphatic hydrocarbons.

The films were wrapped on glass plates, cleaned with toluene if theprimer was toluene based or cleaned with the non-aromatic hydrocarbonsolvent if the primer solution was XPS 6847 based. An 0.00762 centimeter(0.003 inch) bird applicator was used coat a film onto thecorona-discharge treated biaxially oriented polypropylene films. Allfilms casted with the toluene-based primers rippled and puckered only onthe film path, not on the uncoated edges. After about 5 minutes of airdrying in the hood the polypropylene films flattened and returned backto flat and smooth. The XPS-naphthenic based primers did not appear toaffect most of the polypropylene films. One or two of the films showedslight ripple or puckering. They returned back to original shape after 5minutes in the hood. After a total of one hour in the hood the filmswere transported to a vacuum oven for four hours at 40° C. (104° F.) andstored in boxes in standard controlled temperature, controlled humidityconditions for 36 hours.

For this test the adhesive was not applied. The test being directedspecifically to the performance of the primer. The primed films werecontacted with a commercial 3M 2-inch wide tape using a 4-lb. roller.The tape was rolled on with two complete passes. The films were slit1.27 cm (0.5 inch) wide, about 2.54 cm (1 inch) of laminate was peeledapart and put in an Instron Pneumatic Grip using a “T” peelconfiguration. The primer thickness was between 0.000254-0.000501 cm(0.1-0.2 mils). The corona-treated polypropylene film had a thickness ofabout 0.0027-0.0033 cm (1.1-1.3 mils).

The results are set out hereinbelow in Table 2. Some of the samples werealso visually observed and the percent primer failure and an arbitraryadhesive failure scale was utilized for evaluation.

TABLE 2 avg¹ I.D. (pli) solvent primer % primer fail⁴ A(tsu)² 4.36 TOLG1652 3 A(tsd)³ 4.18 TOL G1652 30 B(tsu) 4.34 XPS G1652 B(tsd) 4.06 XPSG1652 C(tsu) 5.12 TOL FG1901 0 C(tsd) 5.12 TOL FG1901 0 D(tsu) 4.34 XPSFG1901 1 D(tsd) 4.12 XPS FG1901 0 E(tsu) 4.2 TOL B52-5 0 E(tsd) 4.9 TOLB52-5 F(tsu) 4.7 XPS B52-5 F(tsd) 5 XPS B52-5 G(tsu) 2.04 TOL NEOPR 70G(tsd) 2.28 TOL NEOPR 38 H⁵ XP NEOPR ¹An average of the five “T” peelInstron readings (pli). A high reading indicates good adhesion of theprimer to the biaxially-oriented polypropylene backing, and a low numberindicates poor adhesion. The actual reading on the ½-inch wide film wasmultiplied by 2 to give the number reported. ²Indicates treated side up,i.e. this tests the adhesion of the primer to the 30 micron coronadischarge-treated surface. ³Treated side down; this tests the adhesionof the primer to the side of the biaxially oriented polypropylene filmnot corona discharge treated. ⁴Against polypropylene film ⁵Could not berun since material would not dissolve in non-aromatic solvent.

As can be seen from formulations B, D, and F, the functionalizedelastomeric block copolymer and the environmentally-friendlynon-aromatic solvent gave excellent results and were uniformly betterthan the commercial neoprene primer by a factor of about two. Thus, theinvention allows the use of an environmentally-friendly solvent withdramatic improvement rather than any sacrifice in quality of theadhesion.

Example 2

In this Example, films were prepared as in Example 1 except when coronatreated, the treatment was at two levels, 40 and 50 dynes. Also in thisExample, the prime surface was further coated with an adhesiveformulation to simulate an actual commercial tape application. Theadhesive formulation was as follows:

D1107 100 parts Wingtack ® 95 100 parts IRGANOX ® 1010 1 part

D1107 is KRATON® D1107 which is a unhydrogenatedstyrene-isoprene-styrene ABA block copolymer having approximately 10,800molecular weight end-blocks with total molecular weight (polystyreneequivalent molecular weight) of about 230,000 made by coupling with adi-functional coupling agent. The above ingredients were dissolved so asto give a 40% solids concentration in toluene or the non-aromatichydrocarbon solvent as indicated in the following table. The solutionswere casted on top of the primed films prepared as set out in Example 1.Compositions are shown hereinbelow in Table III.

TABLE 3 Materials A B C D E F G⁸ G1652¹ 7 7 FG1901² 7 7 B52-5³ 7Bayprene⁴ 3.5 Nipol⁵ 3.5 Toluene⁶ 93 — 93 — 93 93 XPS 6847⁷ — 93 — 93 —— ¹KRATON ® R G1652 elastomeric ABA block copolymer; 28% styrene SEBS;mid-block hydrogenated 1-2 addition polymerization butadiene ²KRATON ®G1652 maleated to give about 2 weight percent functional component.³KRATON ® G1652 maleated to give about 5 weight percent functionalcomponent. ⁴Neoprene rubber. ⁵Neoprene rubber. ⁶Aromatic solvent.⁷Commercial non-aromatic hydrocarbon containing predominantlymethyl-cyclohexane. ⁸No primer.

After the primers were casted onto corona-treated or untreated sides thefilms were hood-dried for one hour and then transferred to a vacuum ovenwith drying continued at 40° C. (104° F.) for four hours. The thicknessof the dried primers averaged about 0.00051 cm (0.2 mils). Then theprimers were casted with the adhesive formulation at 0.0038 cm (1.5mils) thick on average and dried under the same conditions as theprimers. The films were annealed in the same manner as the Example 1films for 24 hours at controlled temperature and controlled humidityconditions and tested using an Instron testing machine (“T” peelconfiguration). Results are shown hereinafter in Table 4.

TABLE 4 “T” Peel Results avg¹ (pli) solvent primer A (treated, 40 dynes)3.9 TOL G1652 A (treated, 56 dynes) 2.9 TOL G1652 A (not treated) 4.3TOL G1652 B (treated, 40 dynes) 4.1 XPS G1652 B (treated, 56 dynes) 3.8XPS G1652 B (not treated) 5.6 XPS G1652 C (treated, 40 dynes) 5.8 TOLFG1901 C (treated, 56 dynes) 5.4 TOL FG1901 C (not treated) 5.7 TOLFG1901 D (treated, 40 dynes) 5.4 XPS FG1901 D (treated, 56 dynes) 5.7XPS FG1901 D (not treated) 4.3 XPS FG1901 E (treated, 40 dynes) 5.5 TOLB52-5 E (treated, 56 dynes) 5.8 TOL B52-5 E (not treated) 3.3 TOL B52-5F (treated, 40 dynes) 3 TOL neopr F (treated, 56 dynes) 3 TOL neopr F(not treated) 2.9 TOL neopr G (treated, 40 dynes) 5.6 NA None ¹Anaverage of the five “T” peel Instron readings as in Example 1. A highreading indicates good adhesion of the primer to the biaxially-orientedpolypropylene backing chemical and a low number indicates poor adhesion.

This Example shows that the apparent advantage for the invention as setout in Example 1 where the primer was simply tested by itself isconfirmed in the formulation of an actual tape with the adhesive placedon the primed surface. That is, a non-aromatic solvent can be used forboth the primer and the adhesive to give a composition which is not onlyenvironmentally friendly in its manufacture but also performs almosttwice as well as the control (Run F with the commercial NEOPRENE). Whiletoluene was used for convenience in applying the adhesive, theenvironmentally friendly solvent used for the primer can be used for theadhesive too.

While this invention has been described in detail for purposes ofillustration, it is not construed as limited thereby but is intended tocover all changes and modifications within the spirit and scope thereof.

What is claimed is:
 1. A process comprising: applying a solution consisting of a selectively hydrogenated elastomeric block copolymer having at least two resinous end-blocks of polymerized monovinylaromatic compound and an elastomeric mid-block of a polymerized conjugated diene and a non-aromatic hydrocarbom solvent to a surface of a polyolefin film; and evaporating said solvent to deposit the selectively hydrogenated elastomeric block copolymer as a primer coating on said surface, said primer coating effective as a tie-coat between said polyolefin film and an adhesive.
 2. The process according to claim 1 wherein said hydrogenated elastomeric block copolymer is derived from a copolymer selected from the group consisting of linear styrene-butadiene-styrene and linear styrene-isoprene-styrene.
 3. The process according to claim 2 wherein said end-blocks have a peak molecular weight within the range of 5,000 to 15,000 and wherein said block copolymer contains 13 to 40 weight percent of said styrene and has a total peak molecular weight within the range of 60,000 to 180,000.
 4. The process according to claim 1 wherein said block copolymer has 0.02-5 weight percent, based on the weight of said block copolymer, of a grafted material.
 5. The process according to claim 1 wherein said block copolymer has 0.2-2 weight percent, based on the weight of said block copolymer, of grafted maleic anhydride.
 6. The process according to claim 1 wherein said film is biaxially oriented polypropylene.
 7. The process according to claim 1 said surface of said film has no surface treatment.
 8. The process according to claim 1 wherein said non-aromatic hydrocarbon solvent is methyl cyclohexane.
 9. The process according to claim 1 wherein said solution has 5-10 weight percent concentration of said copolymer.
 10. The process according to claim 9 wherein said hydrogenated elastomeric block copolymer is derived from a linear styrene-butadiene-styrene copolymer wherein said end-blocks have a peak molecular weight within the range of 5,000 to 15,000 and wherein said block copolymer contains 13 to 40 weight percent of said styrene and has a total peak molecular weight of 60,00 to 180,000, and wherein said block copolymer contains 0.2-2 weight percent of grafted maleic anhydride, wherein said film is biaxially oriented polypropylene having no surface treatment and wherein said solvent comprises predominantly methyl cyclohexane. 